Pancreatic Stellate Cells Have Distinct Characteristics From Hepatic Stellate Cells and Are Not the Unique Origin of Collagen-Producing Cells in the Pancreas

Retinoic acid signaling pathway in pancreatic stellate cells: Insight into the anti-fibrotic effect and mechanism

Pancreatic stellate cells (PSCs) are activated following loss of cytoplasmic vitamin A (retinol)-containing lipid droplets, which is a key event in the process of fibrogenesis of chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDCA). PSCs are the major source of cancer-associated fibroblasts (CAFs) that produce stroma to induce PDAC cancer cell growth, invasion, and metastasis. As an active metabolite of retinol, retinoic acid (RA) can regulate target gene expression in PSCs through its nuclear receptor complex (RAR/RXR or RXR/RXR) or transcriptional intermediary factor. Additionally, RA also has extranuclear and non-transcriptional effects. In vitro studies have shown that RA induces PSC deactivation which reduces extracellular matrix production through multiple modes of action, such as inhibiting TβRⅡ, PDGFRβ, β-catenin and Wnt production, downregulating ERK1/2 and JNK phosphorylation and suppressing active TGF-β1 release. RA alone or in combination with other reagents have been demonstrated to have an effective anti-fibrotic effect on cerulein-induced mouse CP models in vivo studies. Clinical trial data have shown that repurposing all-trans retinoic acid (ATRA) as a stromal-targeting agent for human pancreatic cancer is safe and tolerable, suggesting the possibility of using RA for the treatment of CP and PDCA in humans. This review focuses on RA signaling pathways in PSCs and the effects and mechanisms of RA in PSC-mediated fibrogenesis as well as the anti-fibrotic and anti-tumor effects of RA targeting PSCs or CAFs in vitro and in vivo, highlighting the potential therapies of RA against CP and PDAC.

Meflin is a marker of pancreatic stellate cells involved in fibrosis and epithelial regeneration in the pancreas

Pancreatic stellate cells (PSCs) are stromal cells in the pancreas that play an important role in pancreatic pathology. In chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDAC), PSCs are known to get activated to form myofibroblasts or cancer-associated fibroblasts (CAFs) that promote stromal fibroinflammatory reactions. However, previous studies on PSCs were mainly based on the findings obtained using ex vivo expanded PSCs, with few studies that addressed the significance of in situ tissue-resident PSCs using animal models. Their contributions to fibrotic reactions in CP and PDAC are also lesser-known. These limitations in our understanding of PSC biology have been attributed to the lack of specific molecular markers of PSCs. Herein, we established Meflin (Islr), a glycosylphosphatidylinositol-anchored membrane protein, as a PSC-specific marker in both mouse and human by using human pancreatic tissue samples and Meflin reporter mice. Meflin-positive (Meflin+ ) cells contain lipid droplets and express the conventional PSC marker Desmin in normal mouse pancreas, with some cells also positive for Gli1, the marker of pancreatic tissue-resident fibroblasts. Three-dimensional analysis of the cleared pancreas of Meflin reporter mice showed that Meflin+ PSCs have long and thin cytoplasmic protrusions, and are localised on the abluminal side of vessels in the normal pancreas. Lineage tracing experiments revealed that Meflin+ PSCs constitute one of the origins of fibroblasts and CAFs in CP and PDAC, respectively. In these diseases, Meflin+ PSC-derived fibroblasts showed a distinctive morphology and distribution from Meflin+ PSCs in the normal pancreas. Furthermore, we showed that the genetic depletion of Meflin+ PSCs accelerated fibrosis and attenuated epithelial regeneration and stromal R-spondin 3 expression, thereby implying that Meflin+ PSCs and their lineage cells may support tissue recovery and Wnt/R-spondin signalling after pancreatic injury and PDAC development. Together, these data indicate that Meflin may be a marker specific to tissue-resident PSCs and useful for studying their biology in both health and disease. © 2023 The Pathological Society of Great Britain and Ireland.

Genetic lineage tracing reveals stellate cells as contributors to myofibroblasts in pancreas and islet fibrosis

Pancreatic stellate cells (PSCs) are suggested to play an important role in the development of pancreas and islet fibrosis. However, the precise contributions and solid in vivo evidence of PSCs to the fibrogenesis remain to be elucidated. Here, we developed a novel fate-tracing strategy for PSCs by vitamin A administration in Lrat-cre; Rosa26-tdTomato transgenic mouse. The results showed that stellate cells give rise to 65.7% of myofibroblasts in cerulein-induced pancreatic exocrine fibrosis. In addition, stellate cells in islets increase and contribute partly to myofibroblasts pool in streptozocin-induced acute or chronic islet injury and fibrosis. Furthermore, we substantiated the functional contribution of PSCs to fibrogenesis of pancreatic exocrine and islet in PSCs ablated mice. We also found stellate cells' genetic ablation can improve pancreatic exocrine but not islet fibrosis. Together, our data indicates that stellate cells are vital/partial contributors to myofibroblasts in pancreatic exocrine/islet fibrosis.

Senescent Human Pancreatic Stellate Cells Secrete CXCR2 Agonist CXCLs to Promote Proliferation and Migration of Human Pancreatic Cancer AsPC-1 and MIAPaCa-2 Cell Lines

Interactions between pancreatic cancer cells and pancreatic stellate cells (PSCs) play an important role in the progression of pancreatic cancer. Recent studies have shown that cellular senescence and senescence-associated secretory phenotype factors play roles in the progression of cancer. This study aimed to clarify the effects of senescence-induced PSCs on pancreatic cancer cells. Senescence was induced in primary-cultured human PSCs (hPSCs) through treatment with hydrogen peroxide or gemcitabine. Microarray and Gene Ontology analyses showed the alterations in genes and pathways related to cellular senescence and senescence-associated secretory phenotype factors, including the upregulation of C-X-C motif chemokine ligand (CXCL)-1, CXCL2, and CXCL3 through the induction of senescence in hPSCs. Conditioned media of senescent hPSCs increased the proliferation—as found in an assessment with a BrdU incorporation assay—and migration—as found in an assessment with wound-healing and two-chamber assays—of pancreatic cancer AsPC-1 and MIAPaca-2 cell lines. SB225002, a selective CXCR2 antagonist, and SCH-527123, a CXCR1/CXCR2 antagonist, attenuated the effects of conditioned media of senescent hPSCs on the proliferation and migration of pancreatic cancer cells. These results suggest a role of CXCLs as senescence-associated secretory phenotype factors in the interaction between senescent hPSCs and pancreatic cancer cells. Senescent PSCs might be novel therapeutic targets for pancreatic cancer.

Targeting of Smad7 in Mesenchymal Cells Does Not Exacerbate Fibrosis During Experimental Chronic Pancreatitis

OBJECTIVES

Transforming growth factor-β (TGF-β)-mediated accumulation of extracellular matrix proteins such as collagen I is a common feature of fibrosis. Pancreatic stellate cells play an integral role in the pathogenesis of pancreatitis, and their profibrotic ability is mainly mediated by TGF-β signaling. To specifically address the role of fibrogenic cells in experimental pancreatic fibrosis, we deleted Smad7, the main feedback inhibitor of TGF-β signaling in this cell type in mice.

METHODS

A mouse strain harboring a conditional knockout allele of Smad7 (Smad7fl/fl) with the tamoxifen-inducible inducible Col1a2-CreERT allele was generated and compared with wild-type mice challenged with the cerulein-based model of chronic pancreatitis.

RESULTS

Pancreatic stellate cells lacking Smad7 had significantly increased collagen I and fibronectin production and showed a higher activation level in vitro. Surprisingly, the fibrotic index in the pancreata of treated conditional knockout mice was only slightly increased, without statistical significance. Except for fibronectin, the expression of different extracellular matrix proteins and the numbers of fibroblasts and inflammatory cells were similar between Smad7-mutant and control mice.

CONCLUSIONS

There was no clear evidence that the lack of Smad7 in pancreatic stellate cells plays a major role in experimental pancreatitis, at least in the mouse model investigated here.

Hic-5 is required for activation of pancreatic stellate cells and development of pancreatic fibrosis in chronic pancreatitis

Accumulated evidence suggests that activated pancreatic stellate cells (PSCs) serve as the main source of the extracellular matrix proteins accumulated under the pathological conditions leading to pancreatic fibrosis in chronic pancreatitis (CP). However, little is known about the mechanisms of PSC activation. PSCs have morphologic and functional similarities to hepatic stellate cells, which are activated by hydrogen peroxide-inducible clone-5 (Hic-5), a TGF-β1-induced protein. In this study, we investigated whether Hic-5 activates PSCs, which promote pancreatic fibrosis development in CP. Hic-5-knockout and wild type mice were subjected to caerulein injection to induce CP. Hic-5 expression was strongly upregulated in activated PSCs from human CP tissue and from mouse pancreatic fibrosis in caerulein-induced CP. Hic-5 deficiency significantly attenuated mouse pancreatic fibrosis and PSC activation in the experimental murine CP model. Mechanistically, Hic-5 knock down significantly inhibited the TGF-β/Smad2 signaling pathway, resulting in reduced collagen production and α-smooth muscle actin expression in the activated PSCs. Taken together, we propose Hic-5 as a potential marker of activated PSCs and a novel therapeutic target in CP treatment.

Pancreatic Stellate Cells: The Key Orchestrator of The Pancreatic Tumor Microenvironment

Pancreatic cancer is one of the most challenging adenocarcinomas due to its hostile molecular behavior and complex tumor microenvironment. It has been recently postulated that pancreatic stellate cells (PSCs), the resident lipid-storing cells of the pancreas, are important components of the tumor microenvironment as they can transdifferentiate into highly proliferative myofibroblasts in the context of tissue injury. Targeting tumor-stromal crosstalk in the tumor microenvironment has emerged as a promising therapeutic strategy against pancreatic cancer progression and metastasis. This chapter brings a broad view on the biological and pathological role of PSCs in the pancreas, activated stellate cells in the onset of tissue fibrosis, and tumor progression with particular emphasis on the bidirectional interactions between tumor cells and PSCs. Further, potential therapeutic regimens targeting activated PSCs in the pre-clinical and clinical trials are discussed.

Pancreatic Stellate Cells: A Rising Translational Physiology Star as a Potential Stem Cell Type for Beta Cell Neogenesis

The progressive decline and eventual loss of islet β-cell function underlies the pathophysiological mechanism of the development of both type 1 and type 2 diabetes mellitus. The recovery of functional β-cells is an important strategy for the prevention and treatment of diabetes. Based on similarities in developmental biology and anatomy, in vivo induction of differentiation of other types of pancreatic cells into β-cells is a promising avenue for future diabetes treatment. Pancreatic stellate cells (PSCs), which have attracted intense research interest due to their effects on tissue fibrosis over the last decade, express multiple stem cell markers and can differentiate into various cell types. In particular, PSCs can successfully differentiate into insulin- secreting cells in vitro and can contribute to tissue regeneration. In this article, we will brings together the main concepts of the translational physiology potential of PSCs that have emerged from work in the field and discuss possible ways to develop the future renewable source for clinical treatment of pancreatic diseases.

Inter- and intra-tumoural heterogeneity in cancer-associated fibroblasts of human pancreatic ductal adenocarcinoma

Cancer‐associated fibroblasts (CAF) are orchestrators of the pancreatic ductal adenocarcinoma (PDAC) microenvironment. Stromal heterogeneity may explain differential pathophysiological roles of the stroma (pro‐ versus anti‐tumoural) in PDAC. We hypothesised that multiple CAF functional subtypes exist in PDAC, that contribute to stromal heterogeneity through interactions with cancer cells. Using molecular and functional analysis of patient‐derived CAF primary cultures, we demonstrated that human PDAC‐derived CAFs display a high level of inter‐ and intra‐tumour heterogeneity. We identified at least four subtypes of CAFs based on transcriptomic analysis, and propose a classification for human PDAC‐derived CAFs (pCAFassigner). Multiple CAF subtypes co‐existed in individual patient samples. The presence of these CAF subtypes in bulk tumours was confirmed using publicly available gene expression profiles, and immunostainings of CAF subtype markers. Each subtype displayed specific phenotypic features (matrix‐ and immune‐related signatures, vimentin and α‐smooth muscle actin expression, proliferation rate), and was associated with an assessable prognostic impact. A prolonged exposure of non‐tumoural pancreatic stellate cells to conditioned media from cancer cell lines (cancer education experiment) induced a CAF‐like phenotype, including loss of capacity to revert to quiescence and an increase in the expression of genes related to CAF subtypes B and C. This classification demonstrates molecular and functional inter‐ and intra‐tumoural heterogeneity of CAFs in human PDAC. Our subtypes overlap with those identified from single‐cell analyses in other cancers, and pave the way for the development of therapies targeting specific CAF subpopulations in PDAC. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

A Rising Star in Pancreatic Diseases: Pancreatic Stellate Cells

Pancreatic stellate cell (PSC) is a type of pluripotent cell located between pancreatic lobules and the surrounding area of acinars. When activated, PSC can be transformed into myofibroblast-like cell. A number of evidences suggest that activated PSC is the main source of the accumulation of extracellular matrix (ECM) protein under the pathological conditions, which lead to pancreatic fibrosis in chronic pancreatitis and pancreatic cancer. Recent studies have found that PSC also plays an important role in the endocrine cell function, islet fibrosis and diabetes. In order to provide new strategies for the treatment of pancreatic diseases, this paper systematically summarizes the recent researches about the biological behaviors of PSC, including its stem/progenitor cell characteristics, secreted exosomes, cellular senescence, epithelial mesenchymal transformation (EMT), energy metabolism and direct mechanical reprogramming.